Which test should be performed next in a suspected case of late (tertiary) syphilis after negative RPR results?

Which test should be performed next in a suspected case of late (tertiary) syphilis after negative RPR results?

• A. Repeat RPR, then perform VDRL
• B. Treponemal test such as MHA-TP on serum
• C. VDRL on CSF
• D. No laboratory test is positive for late (tertiary) syphilis

Answer: (B)

In a suspected case of late (tertiary) syphilis, following negative results from the Rapid Plasma Reagin (RPR) test, the appropriate next step is to perform a treponemal test such as the Microscopic Agglutination Test for Treponema pallidum (MHA-TP) on serum. During the course of syphilis infection, particularly in its later stages, non-treponemal tests like the RPR may yield false-negative results due to the lack of reagin antibodies in the bloodstream. This phenomenon is more common in late syphilis. Therefore, to confirm a diagnosis of late syphilis, a treponemal test is necessary. These tests detect antibodies that are specific to Treponema pallidum, the causative organism of syphilis, and they remain positive even when non-treponemal tests become negative. Treponemal tests are more sensitive for diagnosing syphilis in its latent and tertiary stages, as they directly target the pathogen rather than the antibodies produced in response to the disease. Thus, using a treponemal test provides reliable confirmation of the presence of syphilis in cases where non-treponemal tests

In a suspected case of late (tertiary) syphilis, following negative results from the Rapid Plasma Reagin (RPR) test, the appropriate next step is to perform a treponemal test such as the Microscopic Agglutination Test for Treponema pallidum (MHA-TP) on serum.

During the course of syphilis infection, particularly in its later stages, non-treponemal tests like the RPR may yield false-negative results due to the lack of reagin antibodies in the bloodstream. This phenomenon is more common in late syphilis. Therefore, to confirm a diagnosis of late syphilis, a treponemal test is necessary. These tests detect antibodies that are specific to Treponema pallidum, the causative organism of syphilis, and they remain positive even when non-treponemal tests become negative.

Treponemal tests are more sensitive for diagnosing syphilis in its latent and tertiary stages, as they directly target the pathogen rather than the antibodies produced in response to the disease. Thus, using a treponemal test provides reliable confirmation of the presence of syphilis in cases where non-treponemal tests